This invention is related to electrosurgical apparatus and in particular to such apparatus for performing laparoscopic, pelviscopic, athroscopic, thoroscopic and like procedures.
Procedures of the foregoing type are experiencing explosive growth in that incisions are kept to a minimum size and thus such procedures facilitate shorter hospital stays and lower costs. For example, with laparoscopic surgery, a patient can return to normal activity within about one week, whereas with procedures where a large incision is made, about a month for full recovery may be required.
It is to be understood that hereinafter and in the claims, whenever the term "laparoscopic" is employed, similar procedures such as pelviscopic, arthroscopic, thoroscopic, and the like where small incisions of the foregoing type are made are also encompassed by this term.
Referring to FIG. 1, there is illustrated a prior art electrosurgical laparoscopic apparatus including a trocar sheath or cannula 10 which is conventionally used to provide a conduit through a patient's skin into the peritoneal cavity. Removably insertable through the trocar sheath is an active electrode probe 12 which includes an electrode 14 and an insulative coating 16 thereon. The tip 18 of the probe may be of different conventional shapes such as needle-shape, hook-shape, spatula-shape, graspers, scissors, etc. and serve various conventional functions such as suction, coagulation, irrigation, pressurized gas, cutting, etc. There are various problems which may arise with respect to the use of the prior art apparatus when used in laparoscopic or like procedures.
A first problem may arise if the insulation 16 on the active electrode is damaged thereby allowing the active current (possibly in the form of arcing) to pass therethrough directly to the patient's tissue (possibly the bowel or colon) whereby peritonitis may set in within several days. The arcing may occur out of the surgeon's field of view which may extend as little as about 2 centimeters from the tip of the active electrode (or the surgical field). The field of view is typically established by illumination and viewing sources inserted through one or more other trocar sheaths at other incisions.
Out of the field of view, there can be many centimeters of insulated active electrode which extend between the trocar sheath and the field of view. This area which is out of the field of view is potentially dangerous. Here, the insulated active electrode may come into contact with the bowel in procedures where the gall bladder, for example, is removed. If the damaged insulation and thus the attendant arcing were to occur within the field of view, the surgeon normally would immediately observe this and deactivate the generator. However, the damaged insulation can and more probably will occur at a site removed from the field of view and thus the surgeon will not be able to observe the arcing which is occurring at the bowel. Furthermore, due to the repeated insertion of the active electrode probe through the trocar sheath, the insulation thereon can be damaged especially since this accessory is quite often pushed through the trocar sheath rather roughly. Hence, damage to the active electrode insulation is particularly a problem in that the full active current may pass through the area of damaged insulation to the return electrode via an unintended site such as the bowel.
A second problem which can arise with the prior art device of FIG. 1 is caused by a capacitive effect where one electrode of the capacitance is the active electrode and the other electrode of the capacitance is the metallic trocar sheath and the dielectric between these elements is the insulation on the active electrode, as can be seen in FIG. 1. Current from the active electrode will be capacitively coupled to the trocar sheath and then returned through the body and the return electrode to the generator. If this current becomes concentrated, for example, between the trocar sheath and an organ such as the bowel, the capacitive current can cause a burn to the organ.
A third potential problem occurs if the active electrode contacts another instrument within the peritoneal cavity such as metallic grippers or the like. The above-mentioned capacitive effect also arises in this situation where the first electrode is the active electrode and the second electrode is the metallic graspers or the like. Thus, where the grippers contact a unintended site, injury may occur.